1. Field of the Invention
High-temperature fuel cells for converting chemical energy into electrical energy. Due to their good efficiency compared with other types of conversion, the electrochemical conversion of energy and the apparatuses required for the purpose are gaining in importance.
The invention relates to the further development of electrochemical high-temperature cells using ceramic solid electrolytes as ion conductors, the cells being required to be substantially independent of the fuel used and to provide a space-saving arrangement.
In a narrower context, it relates to current-transmitting components for conducting current between adjacent shallow, planar, stacked ceramic high-temperature fuel cells containing solid electrolyte based on doped stabilized zirconium oxide, the oxygen electrode of one fuel cell being electrically conductively connected in each case to the fuel electrode of the subsequent fuel cell and the gap between the electrodes being subdivided by a gas-impervious electrically conducting separating plate into two chambers conducting the different gaseous media comprising fuel (CH.sub.4) and oxygen (O.sub.2) carrier.
The invention furthermore relates to a method of producing the current-transmitting components.
2. Discussion of Background
High-temperature fuel cells containing ceramic solid electrolyte are known from numerous publications. The actual components for such cells may have a very wide variety of shapes and dimensions. In order to keep the ohmic voltage losses low, attempts are being made everywhere to keep the thickness of the electrolyte layer as low as possible. The shape and dimensions of the components depend, in addition, on the requirement for the possibility of electrically connecting a plurality of cells in series in order to obtain the terminal voltage needed and to keep the currents comparatively low.
In the case of a stacked arrangement of a plurality of plate-like planar fuel cells resembling the filter press principle, the current has to be conducted perpendicularly to the plane of the plates from the oxygen electrode of one cell to the fuel electrode of the subsequent cell. Electrical connecting links to the electrodes (current collectors) and separating plates (bipolar plates) are necessary for this function as essential components.
The components hitherto known frequently do not meet the modern requirements in relation to the materials used, the design and fabrication, and also the long-term behavior.
The known basic components used for fuel cells are generally distinguished by a comparatively complicated geometry which makes it difficult to construct compact space-saving systems. In particular, a usable configuration which can be achieved with simple fabrication means is lacking for an optimum series connection of the individual cells.
There is therefore a considerable need for further development, simplification and rationalization of the structure and the production of current-carrying basic components and their optimum mutual arrangement, based on ceramic high-temperature fuel cells.
The following documents are cited in relation to the prior art:
O. Antonsen, W. Baukal and W. Fischer, "Hochtemperatur-Brennstoffbatterie mit keramischem Electrolyten" ("High-temperature fuel battery containing ceramic electrolytes"), Brown Boveri Mitteilungen, January/February 1966, pages 21-30, PA0 U.S. Pat. No. 4,692,274 PA0 U.S. Pat. No. 4,395,468 PA0 W. J. Dollard and W. G. Parker, "An overview of the Westinghouse Electric Corporation solid oxide fuel cell program", Extended Abstracts, Fuel Cell Technology and Applications, International Seminar, The Hague, Holland, 26 to 29 Oct. 1987, PA0 F. J. Rohr, High-Temperature Fuel Cells, Solid Electrolytes, 1978, published by Academic Press Inc., pages 431 ff, PA0 D. C. Fee et al., Monolithic fuel Cell Development, Argonne National Laboratory, Paper presented at the 1986 Fuel Cell Seminar, Oct. 26-29, 1986 Tucson, Ariz., U.S. Department of Energy, The University of Chicago.